Validating a value is present for MultiSelect

[anonymous]

What's the best implementation for validating for value <> for unhidden custom fields. I am using DynamicFieldPlugin with MultiSelectFieldPlugin. Here is a sample of my trac.ini:

ci_appls = text ci_appls.clear_on_hide = true ci_appls.format = list ci_appls.hide_when_component = Facility ci_appls.invalid_if = ci_appls.label = Application CIs Affected ci_appls.multiselect = true ci_appls.options = Desk Top|Help Desk Application ci_appls.order = 8 ci_appls.value = ci_appls.show_when_component = Applications ci_facility = text ci_facility.clear_on_hide = true ci_facility.format = list ci_facility.hide_when_component = Applications ci_facility.invalid_if = ci_facility.label = Facility CIs Affected ci_appls.multiselect = true ci_appls.options = Power|Cooling ci_appls.order = 9 ci_appls.value = ci_appls.show_when_component = Facility

The invalid_if does not catch the error.